Many modern industrial processes require the movement of large masses of dry, semi-dry or viscous products from one place to another. For example, coal, sand, gravel, bulk chemicals, crude oil, molasses, plastic resins and many other similar materials must be transported from the place of origin to another place for finishing, weighing, grading, shipping, extruding and the like. Once shipped, such materials must often be moved again to a furnace, compressor, extruder, mixer or the like.
Currently there are four basic methods and structures for moving such materials. These are: Conveyor belts, bucket loaders or scoop systems, screw feeders and vacuum devices. Each of these devices has its limitations. Open conveyor belts are of limited capacity (relative to their size) because of the potential side spillage and also require constant support. If the conveyor belts are of the closed tube type loading and unloading of the tube is a problem solved only at considerable expense and with the use of relatively complex mechanical gears.
The bucket loader or scoop system resembles the well known coal loader type of device in which buckets are mounted on a movable chain or cable which is formed in a closed loop. The buckets are driven by the chain or cable in a closed loop through a loading station and an unloading station. In the least complicated of such system the unloading is accomplished by the bucket turning 180.degree. around a pulley and starting on the return trip. The bucket empties into a large hopper which in turn must be emptied.
The vacuum system operates at very high temperatures and air flows of relatively high velocity and volume. In such a system the noise level tends to be very high and unacceptable by current standards of employee health and safety. In particular such systems must be modified to meet current Federal Regulations in many cases.
The bucket system and the vacuum system are relatively inefficient uses of energy for the mass of material moved. The conveyor belt systems are relatively efficient but require excessive amounts of space to move modest amounts of materials unless the tubular conveyors are used. Screw feeders are slow, heavy and very expensive.
Typical tubular or closed conveyor belt approaches are illustrated in the following U.S. Pat. Nos. N. G. Tribe; 3,358,812; C. O. Davidson; 3,332,537; E. J. Renner; 2,839,181; H. S. Johns; 2,212,024; H. S. Johns; 2,108,488.
Each of the above patents shows a closed tube of circular or rectangular cross-section having a longitudinal seam (i.e., along the direct of motion) which can be opened and closed for loading and unloading. While the structures shown in the above patents are workable, the structures are relatively complex. The conveyor belts or tubes must be relatively resilient and the weight of material transported is limited by the relative strength of the tube along the longitudinal slit; even if the longitudinal slit is above the materials being transported during some part of the cycle. Each of the above noted patents shows another approach to solving the problems inherent in the prior art closed tube structure.